At 12:17 PM 14/06/2010, you wrote:
>Anybody know the difference in price between a
Ventus 2CXM and a 2CX currently?
I think you pay about €25,000 for a complete self launching Solo motor
+ instruments in a DG glider.
Not quite what I asked. The glider differs
structurally from the motorgless glider. Maybe
the DG and Schempp dealers would like to chip in
here with some prices in Euro? Basic airframes
without options would do. Tom, Chris?
However, that's a certified installation. You could pick up a Rotax 2
stroke UL engine or a non certified and otherwise identical Solo for a
lot less, perhaps a quarter of this. That's what you need to compare
with the experimental or uncertified jet or electric motors.
The 2 stroke doesn't do you much good as the
airframe you want to convert needs too many mods,
like maybe a new mainspar and lots of changes in
the engine bay area to restore the strength and
stiffness of the fuselage. Also the uncertified
engine needs a reduction drive, prop, mounting
and extend/retract mechanism. Still so cheap?
The jet doesn't need the first two and the mount
and mechanism is ridiculously light and simple
compared to that for a 2 stroke, as is the engine and even the battery.
I think it was Churchill who said, 2 strokes are the worst form of SLG
powerplant, except for the others that have been tried from time to
time.
I watched a 30 year old PIK self launch over the weekend with its
ancient Rotax 505. It did not have the climb rate of a modern SLG but
it would have used about 2 litres of fuel to get to soaring height
using a motor which any competent lawn mower mechanic could service.
On 20 litres of fuel, the modern 2 stroke SLG will fly about 5.5 km.
There must be a mistake here. I didn't realise
the economy was so stunningly good.
Maybe you mean 5.5Km on 2 l?
I do agree that the Pik20E was a good design as
was the DG400. It also means that we haven't made
much progress in 35 years in 2 stroke SLGs and
arguably have gone backwards. Forcing
manufacturers to go the "certified" Solo when
Rotax stopped production of the certified Rotax 2
strokes was disaster as most of the problems of
the Rotaxes had been worked out. Particularly
when essentially the same engines continued in
production for ultralights. An SLG with a failed
extended engine has a better glide angle than most ultralights anyway.
The Rotax in the Nimbus 3DM has caused few
problems for us and it is 21 years old.
The present crop of 2 stroke or rotary factory
built SLGs seem to have more than their share of
troubles. When they aren't burning the glider to
the ground they are having exhaust system fires,
engine failures or drive belt problems. You
couldn't *give* me a one of them. They also spend
much of their time being non self launching or
even self retrieving. Note the Dr Jack's Blipmaps
guy here a few months ago and his ASH26E or used to be "E".
It takes about 5 minutes to "recharge" the tank. Normally another 20l
can be carried in wing tanks.
I'm undoubtedly wrong here, but all the current breed of electric
motors are going to be permanent magnet motors driven by some fancy
switching regulator and a set of high-tech batteries. I've had a bit
of experience with all three, but would not expect that any one of
these items would last beyond 5 years.
Hopefully Simon Hackett's Tesla electric car will
last longer than that, the electronics and motor
anyway. I suspect the problems with both motors
and electronics have been solved. The only thing
that ought to fail on the power electronics is
the switching MOSFETS. The batteries, no. I think
we have a LONG way to go in batteries.
The magnets in the motor lose power over time, irrespective of the
type of magnet. The hotter they get, the more rapidly they lose power.
The electronics are highly stressed componentsÂ… they're switching
what?.... 30, 40 KVA of power? The best model aero versions don't seem
to last longer than a year or two switching 1 or 2 KVA and in any
case, they're obsolete technology in 3 years. I don't need to mention
the batteries' life span, but any read of a model aero mag has some
"humorous" stories about people losing cars, sheds and houses
recharging them.
We're talking HobbyWorld here. They run the
batteries and everything else beyond prudent
engineering limits to get performance. Like cars
on a racetrack, they will blow things up and get short working life.
Talk to the people down at Temora when they have a model jet
weekend... and ask about the model fire engine which runs around
putting out the fires.
HobbyWorld again. The best of those people don't
seem to have problems that some of the rest seem
to have all the time. I've watched the jet models
locally and they didn't seem to have problems.
I've also bench run the small jets a few times
without problems. Allan Hudson has nearly 30
hours engine running time on his tri jet
installation and most of his problems have been
due to bad and/or contaminated start gas. I'm
sure we'll discover other things that must be
done to assure reliability/long
life/availability.Note the early model jets used
compressed air to spin up and a manual start
sequence. Lately, electric start and FADEC makes
things a lot better. I strongly suspect from my
testing that spark ignition will immensely add to reliability.
I'm sure that electric and jet have a lot to offer, but before you
discard the 2 stroke, there's at least 90 years of development behind
it and at this stage, there's nothing else which gives the same bang
for the buck.
Yeah jets have only been around for 73 years or
so. Small ones at least 60 years(Turbomeca).
There were some small jets for sale on
barnstormers.com recently for less than $20,000
Australian. These are later developments of the
TRS18 that powered the Jet Caproni. I have some
time in that aircraft and Mike Burns has improved
the installation no endin the one at Toc. Ask
Ingo Renner. He loves it and hates 2 stroke SLGs due to their unreliability.
Mike
Borgelt Instruments - manufacturers of quality soaring instruments since 1978
phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
email: mborg...@borgeltinstruments.com
website: www.borgeltinstruments.com
_______________________________________________
Aus-soaring mailing list
Aus-soaring@lists.internode.on.net
To check or change subscription details, visit:
http://lists.internode.on.net/mailman/listinfo/aus-soaring
